1. Field of the Invention
The present invention relates to wrenches and, more particularly, to crescent wrench.
2. Description of the Related Art
Screw bolts and nuts are commonly used to fix parts of machines and furniture. For grasping and turning different sizes of screw bolts or nuts, different sizes of wrenches shall be used. A crescent wrench is an adjustable wrench suitable for grasping and turning different sizes of screw bolts and nuts. FIG. 1 shows a regular commercially available crescent wrench. This structure of crescent wrench comprises a handle 1, a fixed jaw 2 formed integral with one end, namely, the front end of the handle 1, a movable jaw 3 coupled to the front end of the handle 1, and a thumbscrew 5 mounted in an opening 4 in the handle 1 for turning with the thumb to move the movable jaw 3 relative to the fixed jaw 2. By means of rotating the thumbscrew 5 to move the movable jaw 3 relative to the fixed jaw 2, the pitch between the fixed jaw 2 and the movable jaw 3 is adjusted subject to the workpiece to be grasped or turned. This structure of crescent wrench is still not satisfactory in function. When rotating the workpiece, excessive reactive force from the workpiece may cause the thumbscrew 5 to slip.
The present invention has been accomplished to provide a crescent wrench, which eliminates the aforesaid problem. It is the main object of the present invention to provide a crescent wrench, which is automatically adjustable subject to the size of the workpiece to be grasped or turned. It is another object of the present invention to provide a crescent wrench, which can easily be operated to grasp or release the workpiece. It is still another object of the present invention to provide a crescent wrench, which positively transfers applied rotary driving force to the workpiece, causing the workpiece to be positively synchronously rotated with the crescent wrench. It is still another object of the present invention to provide a crescent wrench, which can be arranged into a compacted condition to reduce storage space when not in use.
To achieve these and other objects of the present invention, the crescent wrench comprises a fixed jaw, a transmission gear wheel pivoted to the fixed jaw, a movable jaw coupled to the fixed jaw and meshed with the transmission gear wheel, a sliding track structure formed in the fixed jaw and the movable jaw and adapted to guide movement of the movable jaw horizontally relative to the fixed jaw, and a handle adapted for turning the transmission gear wheel to move the movable jaw horizontally relative to the fixed jaw.